Carburetor throttle valve positioner

ABSTRACT

One embodiment of a downdraft type carburetor has an idle system discharge port that is straddled by the normal idle speed and closed throttle positions of the throttle valve so as to permit idle speed fuel and air flow in one position and no flow in the other position; a third beyond normal idle, or fast idle speed position is provided for engine startup; another embodiment has a conventional idle system with a transfer port cooperating with the edge of the throttle valve so as to permit normal idle speed fuel and air flow in one position and a less combustible mixture flow in a second position, as well as a third beyond normal idle engine hot start position; the three positions of each embodiment are controled by a servo operatively engaging the throttle valve; the servo operation is controlled by intake manifold vacuum to initially close the throttle valve upon engine shut off, with a subsequent return of the throttle valve to its fast idle position for engine restarting, or to return the throttle valve to a normal idle position upon release of the vehicle accelerator pedal during engine operation.

[451 Sept. 25, 1973 CARBURETOR THROTTLE VALVE POSITIONER PrimaryExaminer-Al Lawrence Smith Attorney-Keith L. Zerschling et al.

[75] Inventors: Robert S. Harrison, Detroit; Harold Marcum, Dearborn,both of Mich.

[57] ABSTRACT One embodiment of a downdraft type carburetor has [73]Assignee: Ford Motor Company,

Dearborn,

Mich.

an idle system discharge port that is straddled by the normal idle speedand closed throttle positions of the [22] Filed: Aug. 7, 1972 throttlevalve so as to permit idle speed fuel and air flow in one position andno flow in the other position;

[21] Appl. No.: 278,674

a third beyond normal idle, or fast idle speed position Related US.Application Data [63] Continuation-in-part of Ser. No.

is provided for engine startup; another embodiment has 159,892, July 6,

a conventional idle system with a transfer port cooperating with theedge of the throttle valve so as to permit normal idle speed fuel andair flow in one position and a less combustible mixture flow in a secondposition, as well as a third beyond normal idle engine hot startposition; the three positions of each embodiment are controled by aservo operatively engaging the throttle valve; the servo operation iscontrolled by intake manifold vacuum to initially close the throttlevalve upon engine shut off, with a subsequent return of the throttlevalve to its fast idle position for engine restarting, or to ReferencesCited UNITED STATES PATENTS return the throttle valve to a normal idleposition upon release of the vehicle accelerator pedal during engine3,618,582 Gerlitz.... 3,491,737 1/1970 Burnia.... 3,603,297 9/1971Sherwin.....................t.

O BXB D m um 3 CARBURETOR THROTTLE VALVE POSITIONER This application isa continuation-in-part of U.S.- Ser.No. 159,892, filed July 6, 1971,Robert S. Harrison and Harold E. Marcum, Carburetor Throttle ValvePositioner, and having a common assignee.

This invention relates, in general, to means for controlling themovement of the throttle valve of'a carburetor. More particularly, itrelates to a vacuum and electrically controlled power means to controlfuel and air flow through a carburetor to prevent engine dieseling andminimize the passage of unburned hydrocarbons into the atmosphere.

The problem of engine dieseling after the engine has been shut off isrecognized. The vacuum signal still present in the carburetor throttlebore below the throttle valve pulls idle system fuel and air into thehot combustion chamber such that combustion is maintained for a fewseconds or longer after the engine is shut off. This naturally isundesirable.

This invention provides a carburetor throttle valve construction that ldepending upon the embodiment, permits a full closing of the throttlevalve upon engine shutdown either to reduce the fuel flow to a level notsustaining engine operation, or shut off all fuel and air flow; or (2) acurb idle position for normally maintaining the engine at a normalidling speed; or (3) a faster idle position for the leaner start of ahot engine. Throttle return delay means is also provided to only slowlyclose the throttle valve during engine deceleration, to dry out thethrottle bore.

The invention in one embodiment provides a construction in which theidle system discharge port is straddled by the throttle valve in itsfully closed and engine idle speed positions so that when the throttlevalve is positioned for normal idle speed operation, idle fuel and airflow can be obtained in the conventional manner; however, when thethrottle valve is moved to its fully closed position, all fuel and airflow is terminated.

In another embodiment, a conventional idle system is provided, and theedge of the throttle valve cooperates with a transfer port such thatwhen the throttle valve is moved to a fully closed position, the idlechannel signal is bled to reduce idle system fuel flow below a levelthat will sustain the engine running.

The invention provides suitable apparatus for moving the throttle valveto its various positions to prevent engine dieseling and the emission ofunburned hydrocarbons into the exhaust system, while at the same timeproviding good starting.

It is one of the objects of the invention, therefore, to provide acarburetor with a throttle valve positioner that will prevent enginedieseling and minimize the passage of unburned hydrocarbons into theexhaust system or atmosphere, and will reposition the throttle valve fora fast idle restart upon engine shutdown.

It is also an object of the invention to provide the throttle valve of acarburetor with a servo that is controlled by manifold vacuum and asolenoid controlled stop to at times close the throttle valve beyond itsnormal idle position to reduce or completely shut off all flow of fuelto the engine cylinders, while at other times positioning the throttlevalve to a beyond idle position for a better engine start.

It is a still further object of the invention to provide a carburetorwith a multi-position throttle valve servo actuator, the servo beingvacuum and solenoid controlled, the solenoid being controlled by anelectrical circuit including the engine ignition key.

Other objects, features and advantages of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawings illustrating a preferred embodiment thereof;wherein,

FIG. 1 shows a cross-sectional view of a portion of a carburetorembodying the invention;

FIG. la is a cross-sectional view of a modification;

FIG. 2 is a cross-sectional view taken on a plane indicated by andviewed in the direction of the arrows 2-2 of FIG. 1; and,

FIG. 3 is a cross-sectional view of a modification.

FIG. 1 illustrates a portion 10 of a downdraft type carburetor, althoughit will be clear as the description proceeds that the invention isequally applicable to other types of carburetors, such as updraft orsidedraft, for example. More particularly, the carburetor is providedwith a main body portion 12 having a cylindrical bore 14 containing theconventional venturi, not shown, in an air/fuel induction passage 16.The latter is open at its upper end 18 to air at essentially atmosphericpressure passing through the conventional air cleaner, not shown. At itslower end 20, passage 16 is adapted to be connected to an engine intakemanifold, from which the air and fuel mixture passes to the enginecylinders, not shown, in a known manner.

The flow of air and fuel through induction passage 16 is controlled inthis instance by a conventional throttle valve 22. The latter isrotatably mounted on a shaft 24 fixed for rotation in the side walls ofbody 12, in a known manner. A main fuel system is not shown, since itcan be any of many known types. The fuel would be inducted into passage16 above the throttle valve in a known manner as a function of therotation of the valve from its fully closed full line position shown toits wide open nearly vertical position, by the change in vacuum signal.

The carburetor also contains an idle system for supplying the necessaryfuel and air to the engine cylinders during engine idling speedoperation. This air and fuel is provided through the bypass passage 26past an adjustable needle valve 28 and through an orificed dischargeport 30 into induction passage 16.

It will be noted in this instance that the discharge end of the idlesystem is located so as to be straddled by the throttle valve betweenits fully closed position 34 and its curb idle or engine idle speedsetting 36 shown in full lines. It will be clear that in the fullyclosed position 34, the vacuum existing below the throttle valve is cutoff from the idle passage 26, and, therefore, no fuel or air will flowat this time as passage 26 is at ambient or atmospheric pressure at bothends. It will also be seen that when the throttle valve is positioned inits normal idle speed position 36, the discharge orifice 30 is subjectedto the vacuum signal below the throttle valve so as to cause the desiredamount of fuel and air to pass through the idle system to maintain theengine at the preset idling speed. A further fast idle or beyond normalidle position 37 is provided for hot engine starting purposes, as willbe explained more clearly later.

FIG. la shows an alternative arrangement in which the invention isadapted for use with a conventional idle system. In this case, the fuelflow is reduced below a level sustaining engine operation, upon engineshutdown, as opposed to completely shutting off flow as described inconnection with FIG. 1. More particularly, FIG. 1a shows a conventionalidle system for supplying the necessary fuel and air to the enginecylinders around the throttle valve during engine idling and off idlespeed operation. A bypass passage or channel 26 contains the usualtransfer port 27 and a discharge port 30' controlled by an adjustableneedle valve 28'.

The transfer port 27 is located so that its lower edge is aligned withthe edge of the throttle valve plate in its closed full line position34'. Alternatively, if desired, the transfer port can be locatedvertically in other positions relative to the throttle plate edge whenthe latter is in the closed position. The dotted line positions 36' and37' on the other hand, indicate respectively the idle speed and fastidle speed positions of the throttle valve.

It will be clear that in the closed position 34', the idle passage areaexposed to the vacuum existing below the throttle valve is reduced fromthat when the throttle valve is in position 36, for example. Therefore,a lower quantity of fuel will flow at this time as the area of thetransfer port 27 above the throttle valve edge subjects passage 26 to anambient or atmospheric pressure bleed. The idle fuel/air mixtureflowable past the needle valve at this time, therefore, is selected tobe too lean to support combustion.

It will also be seen that when the throttle valve is positioned in itsidle speed dotted line position 36, the transfer port area subjected tothe vacuum signal below the throttle valve is increased so as toincrease the amount of fuel to pass through the idle system to an amountneeded to maintain the engine at idling speed.

Returning now to both FIGS. 1 and 1a, to move the throttle valves 22, 22to the two positions, to accomplish the above, a lever or link 38 isfixed on or formed integral with throttle valve shaft 24, 24' forrotation with it, a tension spring 40 biasing lever 38 in a clockwisedirection at all times to bias the throttle valve t its closed position34, 34'.

Lever 38 is adapted to be moved clockwise to the right, as seen in FIGS.1 and la, to rotate the throttle valve clockwise to its normal idlespeed position 36, or to the fast engine idle speed position 37, by aservo 42. The latter includes an open shell type housing 44 closed by astepped diameter cover 45. A flexible annular diaphragm 46 is securedbetween the housing and cover and extends across the hollow interiordefined between the two to divide it into an atmospheric pressurechamber 48 and a vacuum chamber 50. A vacuum line 52 opens into chamber50, while chamber 48 communicates with the atmosphere through holes 54in cover 45.

Fixedly secured to diaphragm 46 by a pair of retainers 56 and 58 is afirst plunger 60 having a central bore or passage 62. A second nylonplunger 64 has a central recess 66 that permits it to be mounted overplunger 60 in a telescopically slidable manner. An internal shoulder 65on plunger 64 prevents total separation of the plungers, but permitssliding to provide the clearance shown. The end of plunger 64 extendsslidable through an opening 67 formed in cover 45.

A light spring 68 biases the two plungers 60 and 64 apart to the extremeposition shown. Plunger 64 is hatshaped in cross section for theattachment thereto, by any suitable means, of an annular screen-typecollapsible dirt filter 70. An O-ring type seal 74 is installed in theend of recess 66 for the seating at times of it against the adjacent endof plunger 60, by the throttle return spring 40.

Plunger 64, as best seen in FIG. 2, has a number of slotted or flutedportions 76 providing air passages 78 connecting the air holes 54 andplunger passage 62 when plunger 60 is not against O-ring seal 74.

Servo chamber 50, on the otherhand, is formed to contain one end of amain spring 80 seated at its opposite end against diaphragm retainer 56.The spring normally biases the diaphragm and both plungers 60 and 64 tothe right to contact link 38, if the vehicle accelerator pedal is notdepressed and the engine inoperative, to force throttle valve 22 to thefast idle, engine start position 37. More fuel vapor exists with a hotengine. Therefore, a greater throttle valve opening provides more airflow to produce the desired starting air/fuel ratio.

A solenoid 82 is adjustably mounted in housing 44, and has an armature84 movable between the full line position shown and the dotted lineposition, as a function of the operativeness or inoperativeness of theengine. That is, the operation of the solenoid is adapted to be tied inwith the engine ignition system, not shown, so that when the ignitionkey is turned on, for example, an electrical connection is made tosolenoid 82 to energize the same and move armature 84 to the dotted lineposition 86. When the ignition system is shut off, for engine shutdown,deenergization of solenoid 82 causes armature 84 to be retracted by aconventional spring, not shown, to the full line position shown.

While not shown, the above described circuit could be similar to thatshown and fully described in Ser. No. 120,953, Carburetor Throttle ValvePositioner, Robert S. Harrison and Max W. Lunsford. It could include,for example, a known type of ignition key operated switch bridging orbreaking the circuit from a battery to the coil of solenoid 82. When thecoil is energized, armatur'e 84 would be forced rightwardly against theforce of a spring to move the armature to the position 86.

In this case, the dotted line position of solenoid armature 84 stops themovement of plunger 60 in a leftward direction at a point correspondingto the normal idle speed position 36 of throttle valve 22. The full lineposition of armature 84 permits the plungers 60 and 64 to moveleftwardly to the fully closed position 34 of the throttle valve.

The force of spring 80 would be chosen to be greater than that of returnspring 40 so that in its rightwardly extended position, plunger 64 willrotate the throttle valve to the fast idle speed position 37 shown.Manifold vacuum, as will be explained, applied to servo chamber 50 onthe other hand will retract the plungers 60 and 64 sufiicient to allowspring 40 to rotate the throttle valve 22 to its dotted line fullyclosed position 34.

The vacuum to line 52 emanates from an intake manifold vacuum port shownopening into the carburetor body portion 12 below the throttle valve. Itcould equally be tapped directly into the intake manifold portion below.The intake manifold vacuum is sensed in a line 92 through a restrictionor orifice 94 to a vacuum reservoir or accumulator (optional, asdesired) indicated schematically at 66. The orifice 64 preventsmomentary fluctuations in the manifold vacuum from affecting the levelof vacuum in the reservoir 66. More importantly, it prevents a suddendecay in the manifold vacuum from equally suddenly decaying the vacuumin the reservoir 66.

FIG. 3 shows a modified construction in which only a single plunger 88is used instead of the dual plunger arrangement of FIGS. 1 and 2. Theplunger is connected directly to diaphragm retainers 56 and 58. Thiseliminates the time delay function shown in FIGS. 1 and 2, which will'be described now in connection with the operation of the invention.

To summarize briefly before proceeding to the operation, the purpose ofthe throttle positioner is to provide three positions for emissioncontrol; namely, a starting position, in which the throttle valve isopened beyond idle'position to provide a leaner start of a hot engineand yet a good start of a colder engine; secondly, a curb idle positionagainst a solenoid armature to which the throttle valve is returnedafter start and during deceleration operation; and, thirdly, anantidieseling position in which the solenoid armature is retracted uponengine shut-off to permit full closure of the throttle valve, with asubsequent return to the engine start, fast idle position after a slightdelay.

The two constructions of FIGS. 1 and 3 differ only in that the FIG. 1construction also contains a dash pot to delay the closing movement ofthe throttle.

In operation of the FIGS. 1, la and 2 embodiments, the parts are shownin the engine-off condition positioned for a start operation. Thethrottle valve spring 40 has returned the throttle valve link 38 againstthe end of plunger 64. This pushes plunger 64 against the end of plunger60, collapsing filter 48 and seating 0- ring seal 74. The main servospring 80 has positioned the diaphragm retainer 58 against the housingcover 45, the light positioning spring 68 being overcome by the throttlereturn spring 40. This position corresponds to a hot start where thethrottle valve is open beyond the normal idle position, to position 37.

As soon as the engine is cranked, the solenoid armature 84 is moved tothe right to the curb idle position indicated at 86. The initial vacuumbuildup in the intake manifold acting through orifice 94 in the passage92 into servo chamber 50 acts against diaphragm 46 to pull the sameagainst the armature 84.

The throttle valve return spring 40 now pushes the throttle valve link38 against plunger 64 and through the seal 74 plunger 60 to causeplunger 60 to follow the movement of diaphragm 46 to position thethrottle valve at the curb idle position. The holes 54 permitatmospheric air pressure to maintain the diaphragm 46 against thesolenoid armature 84. The plunger 60 being sealed against the seal 74 atthis time prevents a bleed down of the vacuum.

As soon as the throttle valve is moved by the operator to an open,off-idle position, beyond the start position, the light spring 68 cannow move the plunger 64 back to a position to unseat seal 74 fromplunger 60. This permits a bleed down of vacuum from chamber 50 by airentering through holes 54, the filter 70, and the fluted passage 76 intothe passages 78 and 62 past seal 74. This decays the vacuum in chamber50 until spring 80 is able to move the diaphragm 46 against the housing45 and spring 68 moves the plunger 64 outwardly to the free positionindicated.

Assume now a deceleration condition in which the throttle valve isreleased towards the curb idle position 36, and the vehicle is drivingthe engine. Immediately, the throttle valve return spring 40 seats theplunger 64 and seal 74 against plunger 60 to block passages 78 to 62.The throttle valve, however, temporarily stays in the start position 37until the vacuum in chamber 50, acting through the restriction 94 in thesupply line 92 builds up again to a point where it will move thediaphragm 46 to the curb idle position 86. This leans the vacuum signalin the carburetor passage 26, and, therefore, provides less fuel and airflow at this time and better emission control.

Assuming now the engine is shut off, the solenoid armature 84immediately will retract to the anti-dieseling position shown in fulllines. Since the intake manifold vacuum is applied through 92 through arestriction or orifice 96, the vacuum remains in chamber 50 forapproximately two seconds after engine shut-off, which is sufficienttime to permit atmospheric pressure in chamber 48 to move the diaphragm46 to the anti-dieseling position closing the throttle valve. After thetwo seconds, the atmospheric buildup in chamber 50 permits the spring toreposition plunger 60 to the right, and spring 68 will move plunger 64to the right to locate throttle valve 22 for the hot start position 37.

The operation of the FIG. 3 embodiment is essentially the same as theFIGS. 1 and 2 embodiment except that no time delay or dash pot action isprovided upon a return movement of the throttle valve to a normal engineidle speed position.

In brief, manifold vacuum in chamber 50 will always hold diaphragm 46against the armature 84 in a curb idle position, so long as the engineis running. Throttle valve spring 40 will, accordingly, always returnthe link 38 and throttle valve 22 to the curb idle position, without adashpot or time delay action.

The anti-dieseling operation is the same as described in connection withFIG. 1.

Therefore, it will be seen thatthe invention provides a throttle valvepositioner that during normal engine operation permits a normal engineidle speed position; and yet also shuts off all flow of fuel and air tothe engine or reduces the idle system fuel flow and prevents enginedieseling after the engine is shut off, for a period of time sufficientto permit the engine to come to rest; and subsequently repositions thethrottle valve to an attitude providing engine starting.

While the invention has been showed in its preferred embodiments in thedrawing, it will be clear to those skilled in the arts to which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

We claim:

1. A carburetor throttle valve positioner comprising, in combination, anengine carburetor having an induction passage open to atmosphericpressure at one end and adapted to be connected to an engine intake,manifold at the opposite end so as to be subject to engine vacuumvarying in level from ambient atmospheric pressure at engine shutdown toa maximum subatmospheric pressure level during engine decelerationoperating conditions, a throttle valve rotatably mounted across saidpassage and movable from a closed position to an engine idle speedposition and beyond to a wide open throttle position, and return, forcontrolling flow through said passage, and control means to move saidthrottle valve to and between said positions, said control meansincluding first means operatively acting on and biasing said throttlevalve to an open beyond normal engine idle throttle position, secondengine manifold vacuum responsive means operatively acting on said firstmeans permitting return movement at times of said throttle valve to anormal engine idle speedv position during operation of said engine,third movable stop means to prevent return movement of said throttlevalve to a position less open than said normal idle position duringoperation of said engine, and means to withdraw said stop means uponengine shut down to permit movement of said throttle valve to a closedantidieseling position reducing the flow of fuel to the englue.

2. A positioner as in claim 1, including fourth means responsive toengine operation and inoperation for moving said third movable means.

3. A positioner as in claim 2, said fourth means comprising a solenoidmovable upon engine startup to a position operatively preventing closingof said throttle valve beyond normal idle speed position, and movable inresponse to engine shutdown to a position permitting closure of saidthrottle valve.

4. A throttle valve position as in claim 1, said control means includinga vacuum controlled servo having a movable actuator operativelyengagable with said throttle valve and said second means to move saidthrottle valve or be moved thereby, said first means comprising a springoperatively biasing said actuator to position said throttle valve opento an engine start- /beyond engine idle position, conduit means forapplying engine manifold vacuum to said second means to move said secondmeans and actuator to said normal engine idle speed position, said thirdmeans comprising solenoid means having said stop means positioned to beengagable by said second means during engine operation to preventmovement thereof below the normal idle speed position, and retractedupon engine shutdown to a position permitting movement of said secondmeans by manifold vacuum to a position permitting a throttle valveclosed position.

5. A positioner as in claim 4, including time delay means associatedwith said servo to delay the return movement of said second meanstowards said stop means.

6. A positioner as in claim 4, including flow restriction means in saidconduit means whereby decay of vacuum level acting on said second meansat engine shutdown is delayed beyond the time period required foractuation of said solenoid so that said second means and throttle valveinitially move to close said throttle valve upon shutdown of saidengine, to reduce antidieseling fuel flow, and subsequently are moved bysaid spring means to an engine start open beyond normal idle throttlevalve position upon decay of said vacuum level.

1. A carburetor throttle valve positioner comprising, in combination, anengine carburetor having an induction passage open to atmosphericpressure at one end and adapted to be connected to an engine intakemanifold at the opposite end so as to be subject to engine vacuumvarying in level from ambient atmospheric pressure at engine shutdown toa maximum subatmospheric pressure level during engine decelerationoperating conditions, a throttle valve rotatably mounted across saidpassage and movable from a closed position to an engine idle speedposition and beyond to a wide open throttle position, and return, forcontrolling flow through said passage, and control means to move saidthrottle valve to and between said positions, said control meansincluding first means operatively acting on and biasing said throttlevalve to an open beyond normal engine idle throttle position, secondengine manifold vacuum responsive means operatively acting on said firstmeans permitting return movement at times of said throttle valve to anormal engine idle speed position during operation of said engine, thirdmovable stop means to prevent return movement of said throttle valve toa position less open than said normal idle position during operation ofsaid engine, and means to withdraw said stop means upon engine shut downto permit movement of said throttle valve to a closed anti-dieselingposition reducing the flow of fuel to the engine.
 2. A positioner as inclaim 1, including fourth means responsive to engine operation andinoperation for moving said third movable means.
 3. A positioner as inclaim 2, said fourth means comprising a solenoid movable upon enginestartup to a position operatively preventing closing of said throttlevalve beyond normal idle speed position, and movable in response toengine shutdown to a position permitting closure of said throttle valve.4. A throttle valve position as in claim 1, said control means includinga vacuum controlled servo having a movable actuator operativelyengagable with said throttle valve and said second means to move saidthrottle valve or be moved thereby, said first means comprising a springoperatively biasing said actuator to position said throttle valve opento an engine start/beyond engine idle position, conduit means forapplying engine manifold vacuum to said second means to move said secondmeans and actuator to said normal engine idle speed position, said thirdmeans comprising solenoid means having said stop means positioned to beengagable by said second means during engine operation to preventmovement thereof below the normal idle speed position, and retractedupon engine shutdown to a position permitting movement of said secondmeans by manifold vacuum to a position permitting a throttle valveclosed position.
 5. A positioner as in claim 4, including time delaymeans associated with said servo to delay the return movement of saidsecond means towards said stop means.
 6. A positioner as in claim 4,including flow restriction means in said conduit means whereby decay ofvacuum level acting on said second means at engine shutdown is delayedbeyond the time period required for actuation of said solenoid so thatsaid second means and throttle valve initially move to close saidthrottle valve upon shutdown of said engine, to reduce anti-dieselingfuel flow, and subsequently are moved by said spring means to an enginestart open beyond normal idle throttle valve position upon decay of saidvacuum level.